An image forming apparatus, such as an electrophotographic device, and an electrostatic recording device, an image is formed by developing a latent electrostatic image formed on a photoconductor with a toner to form a toner image, transferring the toner image to a recording medium, such as paper, and then fixing the toner image with application of heat. To form a full-color image, typically four colors of the toners, black, yellow, magenta, and cyan, are used for developing, and toner images of these colors are transferred and superimposed on the recording medium, followed by fixing at once with application of heat.
Low temperature fixing has been sought for the purpose of lowering global environmental loads. However, a toner having a low melting point forms aggregates, and forms defective images (especially in a high temperature high humidity environment). Therefore, as a low temperature fixing ability of a toner is improved further, it is very difficult for a conventional toner to attain both low temperature fixing ability and inhibition of aggregation.
For example, there is an attempt to attain both low temperature fixing ability and hot offset resistance by using crystalline polyester in a toner (see PLT 1), but there is no teaching about influence of aggregates of the toner. Moreover, the proposed toner cannot achieve both an ultimate level of low temperature fixing ability of the next generation, and a high level of reduction in aggregation of toner particles in high temperature and high humidity environment, which are aimed in the present invention, and therefore remains a problem.